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Optimising voice quality for voip connections – Siemens GIGASET C475 IP User Manual

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141

Web configurator – configuring the telephone via a PC

Optimising voice quality for VoIP connections

Gigaset C470-475 IP / EN for IM-Ost / A31008-xxxx-xxxx-x-xxxx / web_server.fm / 18.12.07

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Optimising voice quality for VoIP connections

You can make general and connection-specific settings to improve the voice quality for

VoIP telephony.

¤

Open the following Web page:

Settings

¢

Telephony

¢

Audio

.

The voice quality for VoIP connections is mainly determined by the voice codec used for

transferring the data and the available bandwidth of your DSL connection.
In the case of the voice codec, the voice data is digitalised (coded / decoded) and com-

pressed. A "better" codec (better voice quality) means more data needs to be transferred,

i.e. perfect voice data transfer requires a DSL connection with a larger bandwidth.
The following voice codecs are supported by your phone:

G.722

If you register an HDSP capable handset (HDSP= High Definition Sound Performance)

with your base station, the calls you make using the handset via G.722 VoIP connections

will have a fantastic sound quality. Gigaset handsets S67H and SL37H, for e.g., are HDSP

capable.
The broadband speech codec

G.722

works at the same bit rate as G.711 (64 kbit/s per

speech connection) but with a higher sampling rate.

G.711 a law / G.711 µ law

Excellent voice quality (comparable with ISDN). The necessary bandwidth is 64 kbit/s

per voice connection.

G.726

Good voice quality (inferior to that with G.711 but better than with G.729).
Your phone supports G.726 with a transmission rate of 32 kbit/s per voice connection.

G.729

Average voice quality. The necessary bandwidth is less than 8 kbit/s per voice connec-

tion.

Both sides of a phone connection (caller/sender side and receiver side) must use the same

voice codec. The voice codec is negotiated between the sender and the recipient when

establishing a connection.

You can influence the voice quality by selecting (bearing in mind the bandwidth of your

DSL connection) the voice codecs your phone is to use, and specifying the order in which

the codecs are to be suggested when a VoIP connection is established.

Area:

Settings for Bandwidth

The settings in this area influence all VoIP connections (VoIP phone numbers).

Allow 1 VoIP call only

Generally speaking you can make two VoIP calls at the same time on your phone. If,

however, your DSL connection has a narrow bandwidth, there may be problems if two

VoIP calls are made at the same time. The data is no longer transferred properly (long

voice delay, data losses etc.).

¤

Activate

Yes

next to

Allow 1 VoIP call only

to prevent any further parallel VoIP phone

connections being established.

¤

If you wish to permit two VoIP connections, activate the

No

option.

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